THE ABELISAURID THEROPOD MAJUNGATHOLUS ATOPUS IN INDIA: IMPLICATIONS FOR ABELISAUROID PALEOBIOGEOGRAPHY

Given their distribution pattern and the poor Gondwanan Late Cretaceous tetrapod record as a whole, abelisauroid theropod occurrences are paleobiogeographically important. While moderately well known from South America and Madagascar, these dinosaurs have long been represented in India and Africa by only fragmentary specimens. Five small shed theropod crowns (GSI 19991-19995) from the Upper Cretaceous (?Maastrichtian) Lameta Group in Gujarat, India that were referred to cf. Megalosaurus types B and C by Mathur and Srivastava in 1987 possess morphologies similar to the abelisaurid Majungatholus atopus from the Upper Cretaceous of Madagascar, for which several well-preserved dentigerous elements are known. Of particular note, GSI 19991 and 19992 possess the distinct morphology of Majungatholus premaxillary teeth of triangular crown shapes with rounded labial faces, slightly convex lingual faces, and denticulated carinae which are located labially on the crowns. The teeth possess mesial and distal interdenticular sulci that curve basally, causing the denticles to fan toward the crown apices. The teeth show a distal recurvature but the mesial and distal recurvature profiles curve smoothly toward the apices. A stepwise discriminant function analysis (DFA) using squared Mahalanobis distances was run to test the idea that GSI 19991 and 19992 are referable to Majungatholus. The DFA compared the teeth against a dataset comprised of in situ theropod dentitions of known taxonomic affinity. The DFA used seven measured and derived variables recently defined that refer to total crown length, base length and width, basal shape, squatness, mesial curve shape, denticle size, and apex location with respect to crown base. In all cases, the analyses produced statistically significant results of <10 Mahalanobis distance units (MDU) between the mean score for the shed tooth in question and the group centroid of a standard of in situ Majungatholus data. The next nearest group centroid to the Lameta teeth was that of Liliensternus at an average of 131 MDU, which is not a significant result. The morphological congruence of the Lameta teeth with Majungatholus and the statistically robust quantitative test of the hypothesis strongly suggests that this theropod existed not only in Madagascar but also in what is now Gujarat, India, during the last part of the Cretaceous.